Geometric statistics and depth correction. (A) Distribution of the filament aspect ratio (L/W_app). (B) Apparent width W_app as a function of normalized heliocentric position x/R_⊙. The red curve shows the best-fit projection model (Equation (12)), yielding a depth-to-width ratio of a = 1.7. (C) Comparison between the apparent depth (assumed equal to W_app) and the geometrically corrected depth D_LOS, color encoded by heliocentric distance ∣x/R_⊙∣. The dashed line indicates the one-to-one correspondence.